This invention relates to thermally stable polymers comprising polyester chain members derived from at least one 1,3-dihydroxybenzene moiety and at least one aromatic dicarboxylic acid moiety (often referred to hereinafter as resorcinol arylate chain members), a method for their preparation, and multilayer articles made therefrom.
Various polymeric articles have a problem of long term color instability. In many cases this instability is seen as yellowing of the polymer, detracting from its attractiveness and also transparency when the polymer was initially transparent. Loss of gloss can also be an undesirable long term phenomenon.
Yellowing of polymers is often caused by the action of ultraviolet radiation, and such yellowing is frequently designated xe2x80x9cphotoyellowingxe2x80x9d. Numerous means for suppressing photoyellowing have been employed and proposed. Many of these involve incorporation in the polymer of ultraviolet absorbing compounds (UVA""s). For the most part, UVA""s are low molecular weight compounds, which must be employed at relatively low levels, typically up to 1% by weight, to avoid degradation of the physical properties of the polymer such as impact strength and high temperature properties as reflected in heat distortion temperature. Another problem of concern with polymers such as aromatic polycarbonates and addition polymers of alkenylaromatic compounds such as styrene is susceptibility to attack by organic liquids.
One way of protecting a resinous article against photoyellowing and loss of gloss is to apply a coating of a weatherable second polymer, the term xe2x80x9cweatherablexe2x80x9d as used herein signifying resistance to such phenomena. Coatings made from polyesters containing resorcinol arylate units often possess good weatherability properties. The arylate moieties typically contain isophthalate, terephthalate, and especially mixtures of iso- and terephthalate units. Polyesters of resorcinol with mixtures of isophthalate and terephthalate chain members typically have good weatherability properties and may provide protection against photoyellowing when coated over a resinous substrate.
The good weatherability properties of polyesters containing resorcinol arylate units are believed to arise in large part from the screening effect said polymers may provide to ultraviolet (UV) light. On exposure to UV light polymers comprising resorcinol arylate chain members may undergo photochemical Fries rearrangement converting at least a portion of the polymer from polyester chain members to o-hydroxybenzophenone-type chain members. The o-hydroxybenzophenone-type chain members act to screen further UV light and protect UV-sensitive components in a resorcinol arylate-containing composition. The good weatherability properties of polymers comprising resorcinol arylate chain members make them especially useful in blends and in multilayer articles in which said polymers may act as a protecting layer for more sensitive substrate components.
Copolyesters comprising resorcinol iso- and terephthalate polyester chain members in combination with diacid or diol alkylene chain members (so-called xe2x80x9csoft-blockxe2x80x9d chain members) are disclosed in commonly owned U.S. Pat. No. 5,916,997. These copolymers have excellent weatherability and flexibility. Copolyestercarbonates comprising resorcinol iso- and terephthalate polyester chain members in combination with carbonate chain members are disclosed in commonly owned, co-pending application Ser. No. 09/416,529, filed Oct. 12, 1999. These copolymers have excellent weatherability and are compatible with polycarbonates in blends.
Polyesters containing resorcinol arylate chain members have been prepared by melt methods as disclosed in U.S. Pat. No. 4,127,560 and in Japanese Kokai 1/201,326. The methods may provide polyesters containing isophthalate and terephthalate chain members but do not allow the incorporation of greater than 30 mole % terephthalate. In addition, the polyesters obtained have unacceptable color.
Polyesters containing resorcinol arylate chain members have also been prepared by an interfacial method. The interfacial method comprises a solvent mixture containing water and at least one organic solvent substantially immiscible with water. According to U.S. Pat. No. 3,460,961 and Eareckson, Journal of Polymer Science, vol. XL, pp. 399-406 (1959), preparation of resorcinol arylate polyesters with a mixture of iso- and terephthalate chain members is performed by an interfacial method in water and a water-immiscible solvent such as chloroform or dichloromethane using 1:1 stoichiometric ratio of resorcinol to either iso- or terephthaloyl dichloride, or a mixture thereof, in the presence of aqueous sodium hydroxide. The resorcinol is combined with the aqueous sodium hydroxide before addition of acid chlorides, and the reaction is run at pH which is initially high but which decreases as the reaction proceeds. The molecular weight of the polymers is not controlled. The method provides polymer with very high weight average molecular weight (Mw), making the polymer unsuitable for some applications. Furthermore, the polymer has poor thermal stability and loses molecular weight upon thermal treatment.
Multilayer articles containing layers made from resorcinol arylate-containing polyester have been described by Cohen et al., Journal of Polymer Science: Part A-1, vol. 9, 3263-3299 (1971) and in U.S. Pat. No. 3,460,961. The polyester was made either in solution or by an interfacial process. The solution method requires the use of a stoichiometric amount of an organic base, such as a tertiary amine, which must be isolated and recovered for reuse in any economical, environmentally friendly process. Both methods produce thermally unstable polyester which can only be applied by solution coating followed by evaporation of the solvent to make a multilayer article. This solution coating method has numerous deficiencies, some of which are mentioned in the Cohen et al. paper at page 3267: namely, the necessity to use high priced and toxic solvents, the inherently low concentration of the arylate polymer in the solvent and the tendency of the solutions to gel. Accordingly, the described polyesters were considered xe2x80x9cunacceptable coating candidatesxe2x80x9d.
Japanese Kokai 1/199,841 discloses articles having a substrate layer comprising at least 90 mole percent poly(ethylene terephthalate) and a gas barrier coating layer which is a polyester of resorcinol and a minimum of 50 mole % isophthalic acid, optionally with copolyester units derived from another dicarboxylic acid such as terephthalic acid, naphthalenedicarboxylic acid or various other specifically named dicarboxylic acids. The disclosed articles may be prepared by a series of operations including co-injection molding. However, the only types of articles disclosed are bottles, which are produced from a co-injection molded parison by subsequent blow molding. Larger articles, such as external automobile body parts, are not disclosed and no method for their production is suggested, nor are articles in which the substrate layer is anything other than poly(ethylene terephthalate). In addition, the resorcinol isophthalate polyesters were prepared either by melt methods which do not allow the incorporation of greater than 30 mole % terephthalate and give polyester with unacceptable color, or by the interfacial method which produces thermally unstable polyester.
It remains of interest, therefore, to develop a method for preparing weatherable, solvent resistant multilayer articles which are capable of use for such varied purposes as body parts for outdoor vehicles and devices such as automobiles. There is also a particular need for polymers comprising resorcinol arylate chain members having controlled molecular weight, high thermal stability, and low color. There is also a particular need for polymers comprising resorcinol arylate chain members that can be processed using typical melt processing techniques.
The present inventors have identified the primary source of poor thermal stability in polymers comprising resorcinol arylate polyester chain members prepared by the interfacial method, and have discovered a method to prepare said polymers in thermally stable form with controlled molecular weight. The new method also allows the preparation of virtually colorless polymers comprising resorcinol arylate polyester chain members.
In one of its aspects the present invention provides an interfacial method for preparing polymers comprising resorcinol arylate polyester chain members substantially free of anhydride linkages linking at least two mers of the polymer chain, comprising the steps of:
(a) combining at least one resorcinol moiety and at least one catalyst in a mixture of water and at least one organic solvent substantially immiscible with water; and
(b) adding to the mixture from (a) at least one dicarboxylic acid dichloride while maintaining the pH between 3 and 8.5 through the presence of an acid acceptor, wherein the total molar amount of acid chloride groups is stoichiometrically deficient relative to the total molar amount of phenolic groups.
In another of its aspects the invention provides a polymer consisting essentially of resorcinol arylate polyester chain members substantially free of anhydride linkages linking at least two mers of the polymer chain, prepared by an interfacial method comprising the above steps.
In yet another of its aspects the invention provides a copolymer consisting essentially of resorcinol arylate polyester chain members in combination with C3-20 straight chain alkylene, C3-10 branched alkylene, or C4-10 cyclo- or bicycloalkylene chain members, substantially free of anhydride linkages linking at least two mers of the polymer chain, prepared by an interfacial method comprising the above steps.
In still another of its aspects the invention provides a copolymer consisting essentially of resorcinol arylate polyester chain members in combination with organic carbonate chain members, substantially free of anhydride linkages linking at least two mers of the polymer chain, prepared by an interfacial method, comprising the above steps.
In one embodiment the present invention comprises an interfacial method for preparing thermally stable polymers comprising resorcinol arylate polyester chain members which derive their thermal stability in large part from being substantially free of anhydride linkages in the polymer chains. In another embodiment the present invention comprises the thermally stable polymers prepared by such an interfacial method.
Thermal stability within the context of the present invention refers to resistance of a polymer to molecular weight degradation under thermal conditions. Thus, a polymer with poor thermal stability shows significant molecular weight degradation under thermal conditions, such as during extrusion, molding, thermoforming, hot-pressing, and like conditions. Molecular weight degradation may also be manifest through color formation and/or in the degradation of other properties such as weatherability, gloss, mechanical properties, and/or thermal properties. Molecular weight degradation can also cause significant variation in processing conditions as the melt viscosity changes.
In one of its aspects the method of the present invention provides thermally stable polymers comprising arylate polyester chain members. Said chain members comprise at least one diphenol residue in combination with at least one aromatic dicarboxylic acid residue. In one embodiment the diphenol residue is derived from a 1,3-dihydroxybenzene moiety, as illustrated in Formula I, commonly referred to throughout this specification as resorcinol or resorcinol moiety. Resorcinol or resorcinol moiety as used within the context of the present invention should be understood to include both unsubstituted 1,3-dihydroxybenzene and substituted 1,3-dihydroxybenzenes unless explicitly stated otherwise. 
In Formula I R is at least one of C1-12 alkyl or halogen, and n is 0-3.
Suitable dicarboxylic acid residues include aromatic dicarboxylic acid residues derived from monocyclic moieties. In various embodiments suitable dicarboxylic acid residues include those derived from isophthalic acid, terephthalic acid, or mixtures of isophthalic and terephthalic acids. Suitable dicarboxylic acid residues also include those derived from polycyclic moieties, illustrative examples of which include diphenyl dicarboxylic acid, diphenylether dicarboxylic acid, and naphthalenedicarboxylic acid, especially naphthalene-2,6-dicarboxylic acid. In some embodiments the aromatic dicarboxylic acid residues are derived from mixtures of isophthalic and/or terephthalic acids as typically illustrated in Formula II. 
Therefore, in one embodiment the present invention provides thermally stable polymers comprising resorcinol arylate polyester chain members as typically illustrated in Formula III wherein R and n are as previously defined: 
Previous interfacial methods for preparing polyesters comprising resorcinol arylate chain members typically provide polymers with poor thermal stability and uncontrolled molecular weight. The present inventors have discovered that a primary reason for poor thermal stability is the presence of anhydride linkages in the backbone of the polyester chain. Typical anhydride linkages are illustrated in Formula IV. Such anhydride linkages link at least two mers in a polymer chain and may arise through combination of two isophthalate or terephthalate moieties or mixtures thereof, although it is to be understood that anhydride linkages in polymers comprising resorcinol arylate chain members may arise through combination of any suitable similar dicarboxylic acid residues or mixtures of suitable dissimilar dicarboxylic acid residues present in a reaction mixture. 
Although the invention is not limited by theory, it is believed that the anhydride linkage represents a weak bond in the polyester chain, which can break under thermal processing conditions to produce shorter chains terminated by acid end-groups. These acid end-groups, in turn, may accelerate the hydrolysis of the arylate moiety, generating additional carboxyl and hydroxyl end-groups, and further contributing to the molecular weight degradation, and loss in other desirable properties. Anhydride linkages may arise through several mechanisms. In one mechanism a carboxylic acid chloride may be hydrolyzed to carboxylic acid when the esterification reaction is run at high pH. The carboxylic acid or corresponding carboxylate may then react with another carboxylic acid chloride to yield an anhydride linkage.
Anhydride linkages may be detected by means known to those skilled in the art such as by 13C nuclear magnetic resonance spectroscopy (NMR). For example, resorcinol arylate polyesters comprising dicarboxylic acid residues derived from a mixture of iso- and terephthalic acids typically show 13C NMR resonances attributed to anhydride at 161.0 and 161.1 ppm (in deuterochloroform relative to tetramethylsilane), as well as resonances for the polymer carboxylic acid and hydroxyl end-groups. After thermal processing (for example, extrusion and/or molding), the polymer molecular weight decreases, and the anhydride resonances typically decrease, while those of the acid and hydroxyl end-groups typically increase.
Anhydride linkages in polymers comprising resorcinol arylate polyester chain members may also be detected by reaction of polymer with a nucleophile, such as a secondary amine. For example, resorcinol arylate polyesters comprising dicarboxylic acid residues derived from a mixture of iso- and terephthalic acids can be dissolved in a convenient solvent, such as dichloromethane, and treated with a secondary amine, such as dibutylamine or diisobutylamine, for several minutes at ambient temperature. Comparison of the starting polymer molecular weight to that after amine treatment typically shows a decrease in molecular weight which can be correlated with the corresponding decrease observed under typical thermal processing conditions. Although the invention is not meant to be limited by theory, it is believed that nucleophiles, such as secondary amine and phenolic, attack anhydride linkages (as opposed to ester linkages) selectively under the reaction conditions. The decrease in molecular weight upon reaction with amine nucleophile is therefore an indication of the presence of anhydride functionality in the polymer.
In one of its aspects the present invention provides an interfacial method for preparing polymers comprising resorcinol arylate polyester chain members substantially free of anhydride linkages, said method comprising a first step of combining at least one resorcinol moiety and at least one catalyst in a mixture of water and at least one organic solvent substantially immiscible with water. Suitable resorcinol moieties comprise units of Formula V: 
wherein R is at least one of C1-12 alkyl or halogen, and n is 0-3. Alkyl groups, if present, are typically straight-chain, branched, or cyclic alkyl groups, and are most often located in the ortho position to both oxygen atoms although other ring locations are contemplated. Suitable C1-12 alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, butyl, iso-butyl, t-butyl, hexyl, cyclohexyl, nonyl, decyl, and aryl-substituted alkyl, including benzyl. In a particular embodiment an alkyl group is methyl. Suitable halogen groups are bromo, chloro, and fluoro. The value for n in various embodiments may be 0-3, in some embodiments 0-2, and in still other embodiments 0-1. In one embodiment a resorcinol moiety is 2-methylresorcinol. In another embodiment the resorcinol moiety is an unsubstituted resorcinol moiety in which n is zero.
The method further comprises combining at least one catalyst with the reaction mixture. Said catalyst may be present in various embodiments at a total level of 0.1 to 10 mole %, and in some embodiments at a total level of 0.2 to 6 mole % based on total molar amount of acid chloride groups. Suitable catalysts comprise tertiary amines, quaternary ammonium salts, quaternary phosphonium salts, hexaalkylguanidinium salts, and mixtures thereof. Suitable tertiary amines include triethylamine, dimethylbutylamine, diisopropylethylamine, 2,2,6,6-tetramethylpiperidine, and mixtures thereof. Other contemplated tertiary amines include N-C1-C6-alkyl-pyrrolidines, such as N-ethylpyrrolidine, N-C1-C6-piperidines, such as N-ethylpiperidine, N-methylpiperidine, and N-isopropylpiperidine, N-C1-C6-morpholines, such as N-ethylmorpholine and N-isopropyl-morpholine, N-C1-C6-dihydroindoles, N-C1-C6-dihydroisoindoles, N-C1-C6-tetrahydroquinolines, N-C1-C6-tetrahydroisoquinolines, N-C1-C6-benzo-morpholines, 1-azabicyclo-[3.3.0]-octane, quinuclidine, N-C1-C6-alkyl-2-azabicyclo-[2.2.1]-octanes, N-C1-C6-alkyl-2-azabicyclo-[3.3.1]-nonanes, and N-C1-C6-alkyl-3-azabicyclo-[3.3.1]-nonanes, N,N,Nxe2x80x2,Nxe2x80x2-tetraalkylalkylene-diamines, including N,N,Nxe2x80x2,Nxe2x80x2-tetraethyl-1,6-hexanediamine. In various embodiments tertiary amines are triethylamine and N-ethylpiperidine.
When the catalyst consists of at least one tertiary amine alone, then said catalyst may be present in one embodiment at a total level of 0.1 to 10 mole %, in another embodiment at a total level of 0.2 to 6 mole %, in another embodiment at a total level of 1 to 4 mole %, and in still another embodiment at a total level of 2.5 to 4 mole % based on total molar amount of acid chloride groups. In one embodiment of the invention all of the at least one tertiary amine is present at the beginning of the reaction before addition of dicarboxylic acid dichloride to resorcinol moiety. In another embodiment a portion of any tertiary amine is present at the beginning of the reaction and a portion is added following or during addition of dicarboxylic acid dichloride to resorcinol moiety. In this latter embodiment the amount of any tertiary amine initially present with resorcinol moiety may range in one embodiment from about 0.005 wt. % to about 10 wt. %, in another embodiment from about 0.01 to about 1 wt. %, and in still another embodiment from about 0.02 to about 0.3 wt. % based on total amine.
Suitable quaternary ammonium salts, quaternary phosphonium salts, and hexaalkylguanidinium salts include halide salts such as tetraethylammonium bromide, tetraethylammonium chloride, tetrapropylammonium bromide, tetrapropylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium chloride, methyltributylammonium chloride, benzyltributylammonium chloride, benzyltriethylammonium chloride, benzyltrimethylammonium chloride, trioctylmethylammonium chloride, cetyldimethylbenzylammonium chloride, octyltriethylammonium bromide, decyltriethylammonium bromide, lauryltriethylammonium bromide, cetyltrimethylammonium bromide, cetyltriethylammonium bromide, N-laurylpyridinium chloride, N-laurylpyridinium bromide, N-heptylpyridinium bromide, tricaprylylmethylammonium chloride (sometimes known as ALIQUAT 336), methyltri-C8-C10-alkyl-ammonium chloride (sometimes known as ADOGEN 464), N,N,Nxe2x80x2,Nxe2x80x2,Nxe2x80x2-pentaalkyl-alpha, omega-amine-ammonium salts such as disclosed in U.S. Pat. No. 5,821,322; tetrabutylphosphonium bromide, benzyltriphenylphosphonium chloride, triethyloctadecylphosphonium bromide, tetraphenylphosphonium bromide, triphenylmethylphosphonium bromide, trioctylethylphosphonium bromide, cetyltriethylphosphonium bromide, hexaalkylguanidinium halides, hexaethylguanidinium chloride, and the like, and mixtures thereof.
Organic solvents substantially immiscible with water include those which in one embodiment are less than about 5 wt. %, and in another embodiment less than about 2 wt. % soluble in water under the reaction conditions. Suitable organic solvents include dichloromethane, trichloroethylene, tetrachloroethane, chloroform, 1,2-dichloroethane, toluene, xylene, trimethylbenzene, chlorobenzene, o-dichlorobenzene, and mixtures thereof. In a particular embodiment the solvent is dichloromethane.
Suitable dicarboxylic acid dichlorides may comprise aromatic dicarboxylic acid dichlorides derived from monocyclic moieties, illustrative examples of which include isophthaloyl dichloride, terephthaloyl dichloride, or mixtures of isophthaloyl and terephthaloyl dichlorides. Suitable dicarboxylic acid dichlorides may also comprise aromatic dicarboxylic acid dichlorides derived from polycyclic moieties, illustrative examples of which include diphenyl dicarboxylic acid dichloride, diphenylether dicarboxylic acid dichloride, and naphthalenedicarboxylic acid dichloride, especially naphthalene-2,6-dicarboxylic acid dichloride; or from mixtures of monocyclic and polycyclic aromatic dicarboxylic acid dichlorides. In one embodiment the dicarboxylic acid dichloride comprises mixtures of isophthaloyl and/or terephthaloyl dichlorides as typically illustrated in Formula VI. 
Either or both of isophthaloyl and terephthaloyl dichlorides may be present. In some embodiments the dicarboxylic acid dichlorides comprise mixtures of isophthaloyl and terephthaloyl dichloride in a molar ratio of isophthaloyl to terephthaloyl of about 0.25-4.0:1; in other embodiments the molar ratio is about 0.4-2.5:1; and in still other embodiments the molar ratio is about 0.67-1.5:1.
The pH of the reaction mixture is maintained in some embodiments between about 3 and about 8.5, and in other embodiments between about 5 and about 8, throughout addition of the at least one dicarboxylic acid dichloride to the at least one resorcinol moiety. Suitable reagents to maintain the pH include alkali metal hydroxides, alkaline earth hydroxides, and alkaline earth oxides. In some embodiments the reagents are potassium hydroxide and sodium hydroxide. In a particular embodiment the reagent is sodium hydroxide. The reagent to maintain pH may be included in the reaction mixture in any convenient form. In some embodiments said reagent is added to the reaction mixture as an aqueous solution simultaneously with the at least one dicarboxylic acid dichloride.
The temperature of the reaction mixture may be any convenient temperature that provides a rapid reaction rate and a resorcinol arylate-containing polymer substantially free of anhydride linkages. Convenient temperatures include those from about xe2x88x9220xc2x0 C. to the boiling point of the water-organic solvent mixture under the reaction conditions. In one embodiment the reaction is performed at the boiling point of the organic solvent in the water-organic solvent mixture. In another embodiment the reaction is performed at the boiling point of dichloromethane.
The total molar amount of acid chloride groups added to the reaction mixture is stoichiometrically deficient relative to the total molar amount of phenolic groups. Said stoichiometric ratio is desirable so that hydrolysis of acid chloride groups is minimized, and so that nucleophiles such as phenolic and/or phenoxide may be present to destroy any adventitious anhydride linkages, should any form under the reaction conditions. The total molar amount of acid chloride groups includes the at least one dicarboxylic acid dichloride, and any mono-carboxylic acid chloride chain-stoppers and any tri- or tetra-carboxylic acid tri- or tetra-chloride branching agents which may be used. The total molar amount of phenolic groups includes resorcinol moieties, and any mono-phenolic chain-stoppers and any tri- or tetra-phenolic branching agents which may be used. The stoichiometric ratio of total phenolic groups to total acid chloride groups is in one embodiment about 1.5-1.01:1 and in another embodiment about 1.2-1.02:1.
The presence or absence of adventitious anhydride linkages following complete addition of the at least one dicarboxylic acid dichloride to the at least one resorcinol moiety will typically depend upon the exact stoichiometric ratio of reactants and the amount of catalyst present, as well as other variables. For example, if a sufficient molar excess of total phenolic groups is present, anhydride linkages are often found to be absent. In one embodiment a molar excess of at least about 1% and in another embodiment a molar excess of at least about 3% of total amount of phenolic groups over total amount of acid chloride groups may suffice to eliminate anhydride linkages under the reaction conditions. When anhydride linkages may be present, it is often desirable that the final pH be greater than 7 so that nucleophiles such as phenolic, phenoxide and/or hydroxide may be present to destroy any adventitious anhydride linkages. Therefore, in various embodiments the method of the invention may further comprise the step of adjusting the pH of the reaction mixture in one embodiment to between 7 and 12, in another embodiment to between 8 and 12, and in still another embodiment to between 8.5 and 12, following complete addition of the at least one dicarboxylic acid dichloride to the at least one resorcinol moiety. The pH may be adjusted by any convenient method; in one embodiment the pH is adjusted using an aqueous base such as aqueous sodium hydroxide.
Provided the final pH of the reaction mixture is greater than 7, the method of the invention in another embodiment may further comprise the step of stirring the reaction mixture for a time sufficient to destroy completely any adventitious anhydride linkages, should any be present. The necessary stirring time will depend upon reactor configuration, stirrer geometry, stirring rate, temperature, total solvent volume, organic solvent volume, anhydride concentration, pH, and other factors. In some instances the necessary stirring time is essentially instantaneous, for example within seconds of pH adjustment to above 7, assuming any adventitious anhydride linkages were present to begin with. For typical laboratory scale reaction equipment a stirring time may be required in one embodiment of at least about 3 minutes, and in another embodiment of at least about 5 minutes. By this process nucleophiles, such as phenolic, phenoxide and/or hydroxide, may have time to destroy completely any adventitious anhydride linkages, should any be present.
At least one chain-stopper (also referred to sometimes hereinafter as capping agent) may also be present in the method and compositions of the invention. A purpose of adding at least one chain-stopper is to limit the molecular weight of polymer comprising resorcinol arylate polyester chain members, thus providing polymer with controlled molecular weight and favorable processability. Typically, at least one chain-stopper is added when the resorcinol arylate-containing polymer is not required to have reactive end-groups for further application. In the absence of chain-stopper resorcinol arylate-containing polymer may be either used in solution or recovered from solution for subsequent use such as in copolymer formation which may require the presence of reactive end-groups, typically hydroxy, on the resorcinolarylate polyester segments. A chain-stopper may be at least one of mono-phenolic compounds, mono-carboxylic acid chlorides, and/or mono-chloroformates. Typically, the at least one chain-stopper may be present in quantities of 0.05 to 10 mole %, based on resorcinol moieties in the case of mono-phenolic compounds and based on acid dichlorides in the case mono-carboxylic acid chlorides and/or mono-chloroformates.
Suitable mono-phenolic compounds include monocyclic phenols, such as phenol, C1-C22 alkyl-substituted phenols, p-cumyl-phenol, p-tertiary-butyl phenol, hydroxy diphenyl; monoethers of diphenols, such as p-methoxyphenol. Alkyl-substituted phenols include those with branched chain alkyl substituents having 8 to 9 carbon atoms, preferably in which about 47 to 89% of the hydrogen atoms are part of methyl groups as described in U.S. Pat. No. 4,334,053. For some embodiments a mono-phenolic UV absorber is used as capping agent. Such compounds include 4-substituted-2-hydroxybenzophenones and their derivatives, aryl salicylates, monoesters of diphenols, such as resorcinol monobenzoate, 2-(2-hydroxyaryl)benzotriazoles and their derivatives, 2-(2-hydroxyaryl)-1,3,5-triazines and their derivatives, and like compounds. In some embodiments mono-phenolic chain-stoppers are phenol, p-cumylphenol, and resorcinol monobenzoate.
Suitable mono-carboxylic acid chlorides include monocyclic, mono-carboxylic acid chlorides, such as benzoyl chloride, C1-C22 alkyl-substituted benzoyl chloride, toluoyl chloride, halogen-substituted benzoyl chloride, bromobenzoyl chloride, cinnamoyl chloride, 4-nadimidobenzoyl chloride, and mixtures thereof; polycyclic, mono-carboxylic acid chlorides, such as trimellitic anhydride chloride, and naphthoyl chloride; and mixtures of monocyclic and polycyclic mono-carboxylic acid chlorides. The chlorides of aliphatic monocarboxylic acids with up to 22 carbon atoms are also suitable. Functionalized chlorides of aliphatic monocarboxylic acids, such as acryloyl chloride and methacryoyl chloride, are also suitable. Suitable mono-chloroformates include monocyclic, mono-chloroformates, such as phenyl chloroformate, alkyl-substituted phenyl chloroformate, p-cumyl phenyl chloroformate, toluene chloroformate, and mixtures thereof.
A chain-stopper can be combined together with the resorcinol moieties, can be contained in the solution of dicarboxylic acid dichlorides, or can be added to the reaction mixture after production of a precondensate. If mono-carboxylic acid chlorides and/or mono-chloroformates are used as chain-stoppers, they are often introduced together with dicarboxylic acid dichlorides. These chain-stoppers can also be added to the reaction mixture at a moment when the chlorides of dicarboxylic acid have already reacted substantially or to completion. If phenolic compounds are used as chain-stoppers, they can be added in one embodiment to the reaction mixture during the reaction, or, in another embodiment, before the beginning of the reaction between resorcinol moiety and acid chloride moiety. When hydroxy-terminated resorcinol arylate-containing precondensate or oligomers are prepared, then chain-stopper may be absent or only present in small amounts to aid control of oligomer molecular weight.
In another embodiment the invention may encompass the inclusion of at least one branching agent such as a trifunctional or higher functional carboxylic acid chloride and/or trifunctional or higher functional phenol. Such branching agents, if included, can typically be used in quantities of 0.005 to 1 mole %, based on dicarboxylic acid dichlorides or resorcinol moieties used, respectively. Suitable branching agents include, for example, trifunctional or higher carboxylic acid chlorides, such as trimesic acid trichloride, cyanuric acid trichloride, 3,3xe2x80x2,4,4xe2x80x2-benzophenone tetracarboxylic acid tetrachloride, 1,4,5,8-naphthalene tetracarboxylic acid tetrachloride or pyromellitic acid tetrachloride, and trifunctional or higher phenols, such as phloroglucinol, 4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-2-heptene, 4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-heptane, 1,3,5-tri-(4-hydroxyphenyl)-benzene, 1,1,1-tri-(4-hydroxyphenyl)-ethane, tri-(4-hydroxyphenyl)-phenyl methane, 2,2-bis-[4,4-bis-(4-hydroxyphenyl)-cyclohexyl]-propane, 2,4-bis-(4-hydroxyphenylisopropyl)-phenol, tetra-(4-hydroxyphenyl)-methane, 2,6-bis-(2-hydroxy-5-methylbenzyl)-4-methyl phenol, 2-(4-hydroxyphenyl)-2-(2,4-dihydroxyphenyl)-propane, tetra-(4-[4-hydroxyphenylisopropyl]-phenoxy)-methane, 1,4-bis-[(4,4-dihydroxytriphenyl)methyl]-benzene. Phenolic branching agents may be introduced first with the resorcinol moieties whilst acid chloride branching agents may be introduced together with acid dichlorides.
For some applications such as for copolymer formation the resorcinol arylate-containing polymer may remain in solution for subsequent process steps. In other instances such as in the production of resorcinol arylate polyester the polymer will normally be isolated from solution. Therefore, in another embodiment of the invention the resorcinol arylate-containing polymer is recovered from the reaction mixture. Recovery methods are well known to those skilled in the art and may include such steps as acidification of the mixture, for example with phosphorous acid; subjecting the mixture to liquid-liquid phase separation; washing the organic phase with water and/or a dilute acid such as hydrochloric acid or phosphoric acid; precipitating by usual methods such as through treatment with water or anti-solvent precipitation with, for example, methanol, ethanol, and/or isopropanol; isolating the resulting precipitates; and drying to remove residual solvents.
If desired, the resorcinol arylate polymers of the invention may be made by the present method further comprising the addition of a reducing agent. Suitable reducing agents include, for example, sodium sulfite, sodium gluconate, or a borohydride, such as sodium borohydride. When present, any reducing agents are typically used in quantities of from 0.25 to 2 mole %, based on moles of resorcinol moiety.
In one of its embodiments the invention comprises thermally stable resorcinol arylate polyesters made by the present method and substantially free of anhydride linkages linking at least two mers of the polyester chain. In a particular embodiment said polyesters comprise dicarboxylic acid residues derived from a mixture of iso- and terephthalic acids as illustrated in Formula VII: 
wherein R is at least one of C1-12 alkyl or halogen, n is 0-3, and m is at least about 8. In various embodiments n is zero and m is between about 10 and about 300. The molar ratio of isophthalate to terephthalate is in one embodiment about 0.25-4.0:1, in another embodiment about 0.4-2.5:1, and in still another embodiment about 0.67-1.5:1. Substantially free of anhydride linkages means that said polyesters show decrease in molecular weight in one embodiment of less than 30% and in another embodiment of less than 10% upon heating said polymer at a temperature of about 280-290xc2x0 C. for five minutes.
The present invention also encompasses thermally stable copolymers containing segments comprising resorcinol arylate polyester chain members made by the present method and substantially free of anhydride linkages linking at least two mers of the copolymer chain. Thus, in another of its embodiments the present invention comprises thermally stable copolyesters comprising resorcinol arylate polyester chain members in combination with dicarboxylic acid or diol alkylene chain members (so-called xe2x80x9csoft-blockxe2x80x9d segments), said copolyesters being substantially free of anhydride linkages in the polyester segments. Substantially free of anhydride linkages means that the copolyesters show decrease in molecular weight in one embodiment of less than 10% and in another embodiment of less than 5% upon heating said copolyester at a temperature of about 280-290xc2x0 C. for five minutes. Related copolyesters containing soft-block segments are disclosed in commonly owned U.S. Pat. No. 5,916,997.
The term soft-block as used herein, indicates that some segments of the polymers are made from non-aromatic monomer units. Such non-aromatic monomer units are generally aliphatic and are known to impart flexibility to the soft-block-containing polymers. The copolymers include those comprising structural units of Formulas I, VIII, and IX: 
wherein R and n are as previously defined, Z is a divalent aromatic radical, R2 is a C3-20 straight chain alkylene, C3-10 branched alkylene, or C4-10 cyclo- or bicycloalkylene group, and R3 and R4 each independently represent 
wherein Formula IX contributes from about 1 to about 45 mole percent to the ester linkages of the polyester. Additional embodiments of the present invention provide a composition wherein Formula IX contributes in various embodiments from about 5 to about 40 mole percent to the ester linkages of the polyester, and in other embodiments from about 5 to about 20 mole percent to the ester linkages of the polyester. Another embodiment provides a composition wherein R2 represents in one embodiment C3-14 straight chain alkylene, or C5-6 cycloalkylene, and in another embodiment R2 represents C3-10 straight-chain alkylene or C6-cycloalkylene. Formula VIII represents an aromatic dicarboxylic acid residue. The divalent aromatic radical Z in Formula VIII may be derived in various embodiments from at least one of the suitable dicarboxylic acid residues as defined hereinabove, and in some embodiments at least one of 1,3-phenylene, 1,4-phenylene, or 2,6-naphthylene. In various embodiments Z comprises at least about 40 mole percent 1,3-phenylene. In various embodiments of copolyesters containing soft-block chain members n in Formula I is zero.
In various embodiments copolyesters containing resorcinol arylate chain members are those comprising from about 1 to about 45 mole % sebacate or cyclohexane-1,4-dicarboxylate units. In a particular embodiment a copolyester containing resorcinol arylate chain members is one comprising resorcinol isophthalate and resorcinol sebacate units in molar ratio between 8.5:1.5 and 9.5:0.5. In one embodiment said copolyester is prepared using sebacoyl chloride in combination with isophthaloyl dichloride.
In another of its embodiments the present invention comprises thermally stable block copolyestercarbonates comprising resorcinol arylate-containing block segments in combination with organic carbonate block segments. The segments comprising resorcinol arylate chain members in such copolymers are substantially free of anhydride linkages. Substantially free of anhydride linkages means that the copolyestercarbonates show decrease in molecular weight in one embodiment of less than 10% and in another embodiment of less than 5% upon heating said copolyestercarbonate at a temperature of about 280-290xc2x0 C. for five minutes. Related block copolyestercarbonates are disclosed in commonly owned, co-pending application Ser. No. 09/416,529, filed Oct. 12, 1999.
The block copolyestercarbonates include those comprising alternating arylate and organic carbonate blocks, typically as illustrated in Formula X, wherein R and n are as previously defined, and R5 is at least one divalent organic radical: 
The arylate blocks have a degree of polymerization (DP), represented by m, in one embodiment of at least about 4, in another embodiment of at least about 10, in another embodiment of at least about 20 and in still another embodiment of about 30-150. The DP of the organic carbonate blocks, represented by p, is in one embodiment generally at least about 10, in another embodiment at least about 20 and in still another embodiment about 50-200. The distribution of the blocks may be such as to provide a copolymer having any desired weight proportion of arylate blocks in relation to carbonate blocks. In general, the content of arylate blocks is in one embodiment about 10-95% by weight and in another embodiment about 50-95% by weight.
Although a mixture of iso- and terephthalate is illustrated in Formula X, the dicarboxylic acid residues in the arylate blocks may be derived from any suitable dicarboxylic acid residue, as defined hereinabove, or mixture of suitable dicarboxylic acid residues, including those derived from aliphatic diacid dichlorides (so-called xe2x80x9csoft-blockxe2x80x9d segments). In various embodiments n is zero and the arylate blocks comprise dicarboxylic acid residues derived from a mixture of iso- and terephthalic acid residues, wherein the molar ratio of isophthalate to terephthalate is in one embodiment about 0.25-4.0:1, in another embodiment about 0.4-2.5:1, and in still another embodiment about 0.67-1.5:1.
In the organic carbonate blocks, each R5 is independently a divalent organic radical. In various embodiments said radical comprises at least one dihydroxy-substituted aromatic hydrocarbon, and at least about 60 percent of the total number of R5 groups in the polymer are aromatic organic radicals and the balance thereof are aliphatic, alicyclic, or aromatic radicals. Suitable R5 radicals include m-phenylene, p-phenylene, 4,4xe2x80x2-biphenylene, 4,4xe2x80x2-bi(3,5-dimethyl)-phenylene, 2,2-bis(4-phenylene)propane, 6,6xe2x80x2-(3,3,3xe2x80x2,3xe2x80x2-tetramethyl-1,1-spirobi[1H-indan]) and similar radicals such as those which correspond to the dihydroxy-substituted aromatic hydrocarbons disclosed by name or formula (generic or specific) in U.S. Pat. No. 4,217,438.
In some embodiments each R5 is an aromatic organic radical and in other embodiments a radical of Formula XI: 
wherein each A1 and A2 is a monocyclic divalent aryl radical and Y is a bridging radical in which one or two carbon atoms separate A1 and A2. The free valence bonds in Formula XI are usually in the meta or para positions of A1 and A2 in relation to Y. Compounds in which R5 has Formula XI are bisphenols, and for the sake of brevity the term xe2x80x9cbisphenolxe2x80x9d is sometimes used herein to designate the dihydroxy-substituted aromatic hydrocarbons. It should be understood, however, that non-bisphenol compounds of this type may also be employed as appropriate.
In Formula XI, A1 and A2 typically represent unsubstituted phenylene or substituted derivatives thereof, illustrative substituents (one or more) being alkyl, alkenyl, and halogen (particularly bromine). In one embodiment unsubstituted phenylene radicals are preferred. Both A1 and A2 are often p-phenylene, although both may be o- or m-phenylene or one o- or m-phenylene and the other p-phenylene.
The bridging radical, Y, is one in which one or two atoms, separate A1 from A2. In a particular embodiment one atom separates A1 and A2. Illustrative radicals of this type are xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94SOxe2x80x94 or xe2x80x94SO2xe2x80x94, methylene, cyclohexyl methylene, 2-[2.2.1]-bicycloheptyl methylene, ethylene, isopropylidene, neopentylidene, cyclohexylidene, cyclopentadecylidene, cyclododecylidene, adamantylidene, and like radicals.
In some embodiments gem-alkylene (commonly known as xe2x80x9calkylidenexe2x80x9d) radicals are preferred. Also included, however, are unsaturated radicals. In some embodiments the preferred bisphenol is 2,2-bis(4-hydroxyphenyl)propane (bisphenol-A or BPA), in which Y is isopropylidene and A1 and A2 are each p-phenylene. Depending upon the molar excess of resorcinol moiety present in the reaction mixture, R5 in the carbonate blocks may at least partially comprise resorcinol moiety. In other words, in some embodiments of the invention carbonate blocks of Formula X may comprise a resorcinol moiety in combination with at least one other dihydroxy-substituted aromatic hydrocarbon.
Diblock, triblock, and multiblock copolyestercarbonates are encompassed in the present invention. The chemical linkages between blocks comprising resorcinol arylate chain members and blocks comprising organic carbonate chain members may comprise at least one of
(a) an ester linkage between a suitable dicarboxylic acid residue of an arylate moiety and an xe2x80x94Oxe2x80x94R5xe2x80x94Oxe2x80x94 moiety of an organic carbonate moiety, for example as typically illustrated in Formula XII, wherein R5 is as previously defined: 
and (b) a carbonate linkage between a diphenol residue of a resorcinol arylate moiety and a "Parenopenst"Cxe2x95x90O)xe2x80x94Oxe2x80x94 moiety of an organic carbonate moiety as shown in Formula XIII, wherein R and n are as previously defined: 
The presence of a significant proportion of ester linkages of the type (a) may result in undesirable color formation in the copolyestercarbonates. Although the invention is not limited by theory, it is believed that color may arise, for example, when R5 in Formula XII is bisphenol A and the moiety of Formula XII undergoes Fries rearrangement during subsequent processing and/or light-exposure. In one embodiment the copolyestercarbonate is substantially comprised of a diblock copolymer with a carbonate linkage between resorcinol arylate block and an organic carbonate block. In another embodiment the copolyestercarbonate is substantially comprised of a triblock carbonate-ester-carbonate copolymer with carbonate linkages between the resorcinol arylate block and organic carbonate end-blocks.
Copolyestercarbonates with at least one carbonate linkage between a thermally stable resorcinol arylate block and an organic carbonate block are typically prepared from resorcinol arylate-containing oligomers prepared by various embodiments of the invention and containing in one embodiment at least one and in another embodiment at least two hydroxy-terminal sites. Said oligomers typically have weight average molecular weight in one embodiment of about 10,000 to about 40,000, and in another embodiment of about 15,000 to about 30,000. Thermally stable copolyestercarbonates may be prepared by reacting said resorcinol arylate-containing oligomers with phosgene, at least one chain-stopper, and at least one dihydroxy-substituted aromatic hydrocarbon in the presence of a catalyst such as a tertiary amine.
It is believed that the weatherability and certain other beneficial properties of the polymers comprising resorcinol arylate polyester chain members of the invention are attributable, at least in part, to the occurrence of thermally or photochemically induced Fries rearrangement of arylate blocks to yield o-hydroxybenzophenone moieties or analogs thereof which serve as stabilizers to UV radiation. More particularly, at least a portion of resorcinol arylate polyester chain members can rearrange to yield chain members with at least one hydroxy group ortho to at least one ketone group. Such rearranged chain members are typically o-hydroxybenzophenone-type chain members comprising one or more of the following structural moieties 
wherein R and n are as previously defined. The o-hydroxybenzophenone-type chain members resulting from rearrangement of resorcinol arylate chain members can be present in resorcinol arylate polyesters and in resorcinol arylate polyester-containing copolymers, including resorcinol arylate-containing copolyestercarbonates and resorcinol arylate-containing copolyesters containing soft-blocks. It is also contemplated to introduce moieties of the types illustrated in Formulas XIV, XV, and XVI via synthesis and polymerization of appropriate monomers in both homopolymers and copolymers by the method of the present invention. In one embodiment the present invention provides thermally stable polyesters, copolyestercarbonates, and copolyesters comprising structural units represented by Formulas III and XIV, wherein the molar ratio of structural units represented by Formula III to structural units represented by Formula XIV ranges in one embodiment from about 99:1 to about 1:1, and in another embodiment from about 99:1 to about 80:20.
The polymers and copolymers comprising thermally stable resorcinol arylate polyester chain members may also be employed in blends with at least one other polymer, especially polycarbonates (hereinafter sometimes designated xe2x80x9cPCxe2x80x9d), polyesters, copolyestercarbonates, polyarylates, polyetherimides, polyphenylene ethers, and addition polymers. Related blends are disclosed in commonly owned U.S. Pat. No. 6,143,839.
The polycarbonates in the blend compositions of the invention are, for the most part, similar in molecular structure to the carbonate blocks of the block copolyestercarbonate as described hereinabove, with bisphenol-A homo- and copolycarbonates generally being preferred in some embodiments. Polyesters are illustrated by poly(alkylene dicarboxylates), especially poly(ethylene terephthalate) (hereinafter sometimes designated xe2x80x9cPETxe2x80x9d), poly(1,4-butylene terephthalate) (hereinafter sometimes designated xe2x80x9cPBTxe2x80x9d), poly(trimethylene terephthalate) (hereinafter sometimes designated xe2x80x9cPTTxe2x80x9d), poly(ethylene naphthalate) (hereinafter sometimes designated xe2x80x9cPENxe2x80x9d), poly(butylene naphthalate) (hereinafter sometimes designated xe2x80x9cPBNxe2x80x9d), poly(cyclohexanedimethanol terephthalate), poly(cyclohexanedimethanol-co-ethylene terephthalate) (hereinafter sometimes designated xe2x80x9cPETGxe2x80x9d), and poly(1,4-cyclohexanedimethyl-1,4-cyclohexanedicarboxylate) (hereinafter sometimes designated xe2x80x9cPCCDxe2x80x9d), and especially poly(alkylene arenedioates), with poly(ethylene terephthalate) and poly(1,4-butylene terephthalate) being preferred in some embodiments.
Copolyestercarbonates may also be used in blends with polymers comprising resorcinol arylate polyester chain members. Such copolymers comprise, in addition to the organic carbonate units, ester units such as isophthalate and/or terephthalate. The copolyestercarbonates which find use in the blends of the instant invention and the methods for their preparation are well known in the art as disclosed in, for example, U.S. Pat. Nos. 3,030,331; 3,169,121; 3,207,814; 4,194,038; 4,156,069; 4,238,596; 4,238,597; 4,487,896; and 4,506,065.
Polyarylates that may be employed in blends include those known in the art. They often comprise structural units derived from aromatic dihydroxy compounds and aromatic dicarboxylic acid compounds described herein as suitable for preparation of polycarbonates, polyesters, and copolyestercarbonates. In various embodiments polyarylates comprise those with structural units comprising the 1,3-dihydroxybenzene moiety present in the arylate blocks of the copolyestercarbonates, those with structural units comprising any organic dihydroxy compound added in the carbonate block formation step in synthesis of said copolyestercarbonates, and those with structural units comprising both of the aforementioned dihydroxy moieties. Illustrative examples include polyarylates comprising terephthalate and/or isophthalate structural units in combination with one or more of unsubstituted resorcinol, substituted resorcinol, and bisphenol A. The polyetherimide resins useful with the present invention are generically known compounds whose preparation and properties are described in U.S. Pat. Nos. 3,803,085 and 3,905,942.
Suitable addition polymers include homopolymers and copolymers, especially homopolymers of alkenylaromatic compounds, such as polystyrene, including syndiotactic polystyrene, and copolymers of alkenylaromatic compounds with ethylenically unsaturated nitriles, such as acrylonitrile and methacrylonitrile; dienes, such as butadiene and isoprene; and/or acrylic monomers, such as ethyl acrylate. These latter copolymers include the ABS (acrylonitrile-butadiene-styrene) and ASA (acrylonitrile-styrene-alkyl acrylate) copolymers.
In another embodiment the invention encompasses blends of polymers and/or copolymers comprising thermally stable resorcinol arylate polyester chain members with at least two other polymers. Said at least two other polymers may comprise miscible, immiscible, and compatibilized blends including, but not limited to, PC/ABS, PC/ASA, PC/PBT, PC/PET, PC/polyetherimide, polyester/polyetherimide, polyphenylene ether/polystyrene, polyphenylene ether/polyamide, and polyphenylene ether/polyester.
The blend compositions of the invention may be prepared by such conventional operations as solvent blending and melt blending. In some embodiments blend preparation is by melt blending, illustrative examples of which include extrusion. The blends may additionally contain art-recognized additives including, but not limited to, pigments, dyes, impact modifiers, UV screeners, UV absorbers, flame retardants, fillers, stabilizers, heat stabilizers, color stabilizers, flow aids, ester interchange inhibitors, and mold release agents. It is intended that the blend compositions include simple physical blends and any reaction products thereof, as illustrated, for example, by polyester-polycarbonate transesterification products.
Proportions of the polymers comprising resorcinol arylate polyester chain members in such blends are determined chiefly by the resulting proportions of arylate blocks, which most often comprise the active weatherability-improving entities, typical proportions providing about 10-50% by weight of arylate blocks in the blend. In blends where some degree of incompatibility may exist between the polymers comprising resorcinol arylate polyester chain members of the invention and the polycarbonates, polyesters, or addition polymers with which they may be combined, said blends are sometimes not fully transparent. However, transparent blends may often be prepared, if desired, by adjusting the length of the arylate blocks in the polymers comprising resorcinol arylate polyester chain members. The other properties of said blends are generally excellent.
Compositions comprising resorcinol arylate polyester chain members made by various embodiments of the method of the invention typically have significantly lower color, both before and after thermal processing, than related compositions made by melt methods, interfacial methods, and solution methods of the prior art. In particular, melt methods typically provide resorcinol arylate polyester with tan to dark brown color while the present interfacial method provides very lightly colored or essentially colorless polyester. The present compositions may be used in various applications, especially those involving outdoor use and storage, and hence requiring resistance to weathering. Their light transmitting properties are often similar to those of polycarbonates. Thus, they are often substantially transparent and colorless, and may often be employed as substitutes for polycarbonates in the fabrication of transparent sheet material when improved weatherability is mandated.
In another embodiment the present invention comprises multilayer articles comprising a substrate layer comprising at least one thermoplastic polymer, thermoset polymer, cellulosic material, glass, ceramic, or metal, and at least one coating layer thereon, said coating layer comprising at least one polymer comprising structural units derived from at least one 1,3-dihydroxybenzene moiety and at least one aromatic dicarboxylic acid moiety and prepared by methods embodied in the present invention. In the present context a multilayer article is one containing at least two layers. In various embodiments a coating layer comprises at least one thermally stable polymer comprising resorcinol arylate polyester chain members substantially free of anhydride linkages linking at least two mers of the polymer chain. Optionally, the multilayer articles may further comprise an interlayer, for example an adhesive interlayer, between any substrate layer and any thermally stable polymer coating layer. Multilayer articles of the invention include, but are not limited to, those which comprise a substrate layer and a coating layer of said thermally stable polymer; those which comprise a substrate layer with a coating layer of said thermally stable polymer on each side of said substrate layer; and those which comprise a substrate layer and at least one coating layer of said thermally stable polymer with at least one interlayer between a substrate layer and a coating layer. Any interlayer may be transparent, translucent, or opaque, and/or may contain an additive, for example a colorant or decorative material such as metal flake. If desired, an overlayer may be included over the coating layer of thermally stable polymer, for example to provide abrasion or scratch resistance. The substrate layer, coating layer of thermally stable polymer, and any interlayers or overcoating layers are often in contiguous superposed contact with one another.
Within the context of the present invention it should be understood that any coating layer comprising a thermally stable polymer comprising resorcinol arylate polyester chain members may also include polymer comprising o-hydroxybenzophenone or analogous chain members resulting from Fries rearrangement of said resorcinol arylate chain members, for example after exposure of said coating layer to UV-light. Typically, a preponderance of any polymer comprising o-hydroxybenzophenone or analogous chain members will be on that side or sides of said coating layer exposed to UV-light and will overlay in a contiguous superposed layer or layers that polymer comprising unrearranged resorcinol arylate chain members. If it is worn away or otherwise removed, polymer comprising o-hydroxybenzophenone or analogous chain members is capable of regenerating or renewing itself from the resorcinol arylate-containing layer or layers, thus providing continuous protection for any UV-light sensitive layers.
It has been unexpectedly discovered that the presence of at least one stabilizer additive in a coating layer comprising resorcinol arylate polyester chain members may have a beneficial effect on color despite the fact that polymers comprising resorcinol arylate polyester chain members and their Fries rearrangement products themselves protect against photoyellowing. In the present context a stabilizer additive is an additive which provides one or both of lower initial color or additional resistance to weathering, as measured for example by initial yellowness index (YI), or by resistance to yellowing and change in color, when compared to a similar coating without at least one stabilizer additive. In a particular embodiment the stabilizer additive comprises at least one auxiliary color stabilizer additive. In another particular embodiment the stabilizer additive comprises at least one auxiliary light stabilizer additive. In one embodiment the presence of at least one auxiliary UV absorber as stabilizer additive provides additional resistance to weathering, for example as measured by initial yellowness index (YI), or resistance to yellowing and change in color, when compared to a similar coating without at least one auxiliary UV absorber. Since resorcinol arylate-comprising polymers generate UV absorber in situ, it is unexpected that the addition of auxiliary UV absorber would affect the amount of color or yellowness generated.
In various embodiments stabilizer additives include those known in the art. For example, illustrative UV absorbers include, but are not limited to, hydroxybenzophenones, hydroxybenzotriazoles, hydroxybenzotriazines, cyanoacrylates, oxanilides, and benzoxazinones. Illustrative UV absorbers also include nano-size inorganic materials such as titanium oxide, cerium oxide, and zinc oxide, all with particle size less than about 100 nanometers. Illustrative examples of stabilizer additives also include carbodiimides, such as bis-(2,6-diisopropylphenyl)carbodiimide and polycarbodiimides; hindered amine light stabilizers; hindered phenols; phosphites and phosphorous acid. Such stabilizer additives are known in the art and are disclosed in standard reference works such as xe2x80x9cPlastics Additives Handbookxe2x80x9d, 5th edition, edited by H. Zweifel, Hanser Publishers. In some embodiments mixtures of stabilizer additives are particularly effective, especially mixtures of the abovementioned stabilizer additives.
The amount of any stabilizer additive employed is in one embodiment in a range between about 0.0005 wt. % and 10 wt. %, in another embodiment in a range between about 0.001 wt. % and about 10 wt. %, in another embodiment in a range between about 0.04 wt. % and about 8 wt. %, in another embodiment in a range between about 0.1 wt. % and about 6 wt. %, in another embodiment in a range between about 0.2 wt. % and about 5 wt. %, in another embodiment in a range between about 0.5 wt. % and about 5 wt. %, and in still another embodiment in a range between about 1 wt. % and about 5 wt. % based on the weight of resorcinol arylate polymer in a coating layer. A stabilizer additive may be combined with coating layer using known methods. In one embodiment stabilizer additive is at least partially dissolved in a solution with components of a coating layer, and a film of coating layer comprising stabilizer additive is solvent cast. In another embodiment stabilizer additive is at least partially dissolved in a solution and impregnated from said solution into solid or at least partially solid coating layer. In still another embodiment stabilizer additive is combined with coating layer in a melt method such as co-extrusion. If desired, the stabilizer additive may be combined with coating layer in the form of a solution of stabilizer additive, for example in water or organic solvent. In one embodiment an aqueous solution of phosphorous acid is employed as stabilizer additive.
The multilayer articles typically have outstanding initial gloss, improved initial color, weatherability, impact strength, and resistance to organic solvents encountered in their final applications. Said articles may also be recyclable by reason of the compatibility of the discrete layers therein.
The material of the substrate layer in the articles of this invention may be at least one thermoplastic polymer, whether addition or condensation prepared. Thermoplastic polymers include, but are not limited to, polycarbonates, particularly aromatic polycarbonates, polyacetals, polyarylene ethers, polyphenylene ethers, polyarylene sulfides, polyphenylene sulfides, polyimides, polyamideimides, polyetherimides, polyetherketones, polyaryletherketones, polyetheretherketones, polyetherketoneketones, polyamides, polyesters, liquid crystalline polyesters, polyetheresters, polyetheramides, polyetheramides, and polyestercarbonates (other than those employed for the coating layer, as defined hereinafter). In some embodiments polycarbonates and polyesters are preferred. A substrate layer may additionally contain art-recognized additives including, but not limited to, colorants, pigments, dyes, impact modifiers, stabilizers, color stabilizers, heat stabilizers, UV screeners, UV absorbers, flame retardants, fillers, flow aids, ester interchange inhibitors, and mold release agents.
Suitable polycarbonates include homopolycarbonates comprising structural units of the type described for the organic carbonate blocks in the copolyestercarbonates of the invention. In some embodiments the polycarbonates are bisphenol A homo- and copolycarbonates. In various embodiments the weight average molecular weight of the initial polycarbonate ranges from about 5,000 to about 100,000; in other embodiments the weight average molecular weight of the initial polycarbonate ranges from about 25,000 to about 65,000.
The polycarbonate substrate may also be a copolyestercarbonate (other than that copolyestercarbonate employed for the coating layer as defined hereinafter). Such copolymers typically comprise, in addition to the organic carbonate units, ester units such as isophthalate and/or terephthalate. The copolyestercarbonates which find use as substrates in the instant invention and the methods for their preparation are well known in the art as disclosed in, for example, U.S. Pat. Nos. 3,030,331; 3,169,121; 3,207,814; 4,194,038; 4,156,069; 4,238,596; 4,238,597; 4,487,896; and 4,506,065.
Polyester substrates include, but are not limited to, poly(alkylene dicarboxylates), especially poly(ethylene terephthalate), poly(1,4-butylene terephthalate), poly(trimethylene terephthalate), poly(ethylene naphthalate), poly(butylene naphthalate), poly(cyclohexanedimethanol terephthalate), poly(cyclohexanedimethanol-co-ethylene terephthalate), and poly(1,4-cyclohexanedimethyl-1,4-cyclohexanedicarboxylate). Also included are polyarylates as described hereinabove, illustrative examples of which include those comprising structural units derived from bisphenol A, terephthalic acid, and isophthalic acid.
Suitable addition polymer substrates include homo- and copolymeric aliphatic olefin and functionalized olefin polymers (which are homopolymers and copolymers comprising structural units derived from aliphatic olefins or functionalized olefins or both), and their alloys or blends. Illustrative examples include, but are not limited to, polyethylene, polypropylene, thermoplastic polyolefin (xe2x80x9cTPOxe2x80x9d), ethylene-propylene copolymer, poly(vinyl chloride), poly(vinyl chloride-co-vinylidene chloride), poly(vinyl fluoride), poly(vinylidene fluoride), poly(vinyl acetate), poly(vinyl alcohol), poly(vinyl butyral), poly(acrylonitrile), acrylic polymers such as those of (meth)acrylamides or of alkyl(meth)acrylates such as poly(methyl methacrylate) (xe2x80x9cPMMAxe2x80x9d), and polymers of alkenylaromatic compounds such as polystyrenes, including syndiotactic polystyrene. In some embodiments the preferred addition polymers are polystyrenes and especially the so-called ABS and ASA copolymers, which may contain thermoplastic, non-elastomeric styrene-acrylonitrile side chains grafted on an elastomeric base polymer of butadiene and alkyl acrylate, respectively.
Blends of any of the foregoing polymers may also be employed as substrates. Typical blends include, but are not limited to, those comprising PC/ABS, PC/ASA, PC/PBT, PC/PET, PC/polyetherimide, PC/polysulfone, polyester/polyetherimide, PMMA/acrylic rubber, polyphenylene ether-polystyrene, polyphenylene ether-polyamide or polyphenylene ether-polyester. Although the substrate layer may incorporate other thermoplastic polymers, the above-described polycarbonates and/or addition polymers often constitute the major proportion thereof.
The substrate layer in the multilayer articles of this invention may also comprise at least one of any thermoset polymer. Suitable thermoset polymer substrates include, but are not limited to, those derived from epoxys, cyanate esters, unsaturated polyesters, diallylphthalate, acrylics, alkyds, phenol-formaldehyde, novolacs, resoles, bismaleimides, PMR resins, melamine-formaldehyde, urea-formaldehyde, benzocyclobutanes, hydroxymethylfurans, and isocyanates. In one embodiment of the invention the thermoset polymer substrate comprises a RIM material. In another embodiment of the invention the thermoset polymer substrate further comprises at least one thermoplastic polymer, such as, but not limited to, polyphenylene ether, polyphenylene sulfide, polysulfone, polyetherimide, or polyester. Said thermoplastic polymer is typically combined with thermoset monomer mixture before curing of said thermoset.
In one embodiment of the invention a thermoplastic or thermoset substrate layer also incorporates at least one filler and/or pigment. Illustrative extending and reinforcing fillers, and pigments include silicates, zeolites, titanium dioxide, stone powder, glass fibers or spheres, carbon fibers, carbon black, graphite, calcium carbonate, talc, mica, lithopone, zinc oxide, zirconium silicate, iron oxides, diatomaceous earth, calcium carbonate, magnesium oxide, chromic oxide, zirconium oxide, aluminum oxide, crushed quartz, calcined clay, talc, kaolin, asbestos, cellulose, wood flour, cork, cotton and synthetic textile fibers, especially reinforcing fillers such as glass fibers, carbon fibers, and metal fibers, as well as colorants such as metal flakes, glass flakes and beads, ceramic particles, other polymer particles, dyes and pigments which may be organic, inorganic or organometallic. In another embodiment the invention encompasses multilayer articles comprising a filled thermoset substrate layer such as a sheet-molding compound (SMC).
The substrate layer may also comprise at least one cellulosic material including, but not limited to, wood, paper, cardboard, fiber board, particle board, plywood, construction paper, Kraft paper, cellulose nitrate, cellulose acetate butyrate, and like cellulosic-containing materials. The invention also encompasses blends of at least one cellulosic material and either at least one thermoset polymer (particularly an adhesive thermoset polymer), or at least one thermoplastic polymer (particularly a recycled thermoplastic polymer, such as PET or polycarbonate), or a mixture of at least one thermoset polymer and at least one thermoplastic polymer.
Multilayer articles encompassed by the invention also include those comprising at least one glass layer. Typically any glass layer is a substrate layer, although multilayer articles comprising a thermally stable polymer coating layer interposed between a glass layer and a substrate layer are also contemplated. Depending upon the nature of coating and glass layers, at least one adhesive interlayer may be beneficially employed between any glass layer and any thermally stable polymer coating layer. The adhesive interlayer may be transparent, opaque or translucent. For many applications it is preferred that the interlayer be optically transparent in nature and generally have a transmission of greater than about 60% and a haze value less than about 3% with no objectionable color.
Metal articles exposed to UV-light may exhibit tarnishing and other detrimental phenomena. In another embodiment the invention encompasses multilayer articles comprising at least one metal layer as substrate layer. Representative metal substrates include those comprising brass, aluminum, magnesium, chrome, iron, steel, copper, and other metals or alloys or articles containing them, which may require protection from UV-light or other weather phenomena. Depending upon the nature of coating and metal layers, at least one adhesive interlayer may be beneficially employed between any metal layer and any thermally stable polymer coating layer.
Also present in the articles of the invention is at least one coating layer comprising at least one polymer comprising structural units derived from at least one 1,3-dihydroxybenzene moiety and at least one aromatic dicarboxylic acid moiety prepared by methods embodied in the present invention. In various embodiments, suitable coating layers comprise polymers comprising thermally stable resorcinol arylate polyester chain members. In other embodiments suitable coating layers comprise resorcinol arylate polyesters, copolyesters (particularly those containing soft-blocks), copolyestercarbonates, and mixtures thereof. Copolyestercarbonates, when used in both substrate layer and in coating layer, are different from each other in molecular structure. More specifically, when the coating layer contains copolyestercarbonate with resorcinol arylate polyester blocks, then any ester blocks in the substrate copolyestercarbonate layer will typically be derived from the same divalent organic radical as contained in the carbonate blocks.
It is also within the scope of the invention for other polymers to be present which are miscible in at least some proportions with a polymer coating layer comprising at least one thermally stable polymer comprising structural units derived from at least one 1,3-dihydroxybenzene moiety and at least one aromatic dicarboxylic acid moiety. Illustrative examples of at least partially miscible polymers include polyetherimide and polyesters such as PBT, PET, PTT, PEN, PBN, PETG, PCCD, and bisphenol A polyarylate. In one embodiment the coating layer polymer consists essentially of thermally stable resorcinol arylate polyesters, copolyesters, or copolyestercarbonates.
Another aspect of the invention is a method for preparing a multilayer article which comprises applying at least one thermally stable coating layer to a second layer, said second layer comprising at least one thermoplastic polymer, thermoset polymer, cellulosic material, glass, or metal, and said coating layer comprising at least one polymer comprising structural units derived from at least one 1,3-dihydroxybenzene moiety and at least one aromatic dicarboxylic acid moiety, the polymer being substantially free of anhydride linkages linking at least two mers of the polymer chain.
In one embodiment of the invention, at least one thermally stable coating layer is applied to a second layer, which may be the substrate layer or at least one intermediate layer ultimately to be disposed between the coating and substrate layers. An intermediate layer may comprise any of the materials suitable for use as the substrate or coating layer, and may further contain fillers and colorants such as described hereinabove. When necessary, it may be specifically chosen so as to provide good adhesion between substrate and coating layers. Colorants of the previously described types may also be present in the coating layer.
In one embodiment application of the at least one coating layer may be performed by solvent-casting. In another embodiment application of said coating layer comprises fabrication of a separate sheet thereof followed by application to the second layer, or by simultaneous production of both layers, typically in a melt process. Thus, there may be employed such methods as thermoforming, compression molding, co-injection molding, coextrusion, overmolding, blow molding, multi-shot injection molding and placement of a film of the coating layer material on the surface of the second layer followed by adhesion of the two layers, typically in an injection molding apparatus; e.g., in-mold decoration, or in a hot-press. These operations may be conducted under art-recognized conditions.
It is also within the scope of the invention to apply a structure comprising the coating layer and the second layer to a third, substrate layer, which may be, for example, of a thermoplastic, thermoset, or cellulosic material similar or identical to that of the second layer but different from that of the coating layer. This may be achieved, for example, by charging an injection mold with the structure comprising the coating layer and the second layer and injecting the substrate sheet material behind it. By this method, in-mold decoration and the like are possible. Both sides of the substrate layer may receive the other layers, though in some embodiments it may be preferred to apply them to only one side.
The thicknesses of the various layers in multilayer articles of this invention are most often as follows:
substratexe2x80x94at least about 125xcexc (microns), or at least about 250xcexc, or at least about 400xcexc,
coatingxe2x80x94about 2-2,500, or about 10-250, or about 50-175xcexc,
second material, if anyxe2x80x94about 2-2,500, or about 10-250, or about 50-175xcexc,
totalxe2x80x94at least about 125xcexc, or at least about 250xcexc, or at least about 400xcexc.
The articles of this invention are typically characterized by the usual beneficial properties of the substrate layer, in addition to weatherability as may be evidenced by such properties as improved initial gloss, improved initial color, improved resistance to ultraviolet radiation and maintenance of gloss, improved impact strength, and resistance to organic solvents encountered in their final applications. Depending upon such factors as the coating layer/substrate combination, the multilayer articles may possess recycling capability, which makes it possible to employ the regrind material as a substrate for further production of articles of the invention.
Multilayer articles which can be made which comprise thermally stable polymers comprising resorcinol arylate polyester chain members include aircraft, automotive, truck, military vehicle (including automotive, aircraft, and water-borne vehicles), scooter, and motorcycle exterior and interior components, including panels, quarter panels, rocker panels, trim. fenders, doors, decklids, trunklids, hoods, bonnets, roofs, bumpers, fascia, grilles, mirror housings, pillar appliques, cladding, body side moldings, wheel covers, hubcaps, door handles, spoilers, window frames, headlamp bezels, headlamps, tail lamps, tail lamp housings, tail lamp bezels, license plate enclosures, roof racks, and running boards; enclosures, housings, panels, and parts for outdoor vehicles and devices; enclosures for electrical and telecommunication devices; outdoor furniture; aircraft components; boats and marine equipment, including trim, enclosures, and housings; outboard motor housings; depth finder housings, personal water-craft; jet-skis; pools; spas; hot-tubs; steps; step coverings; building and construction applications such as glazing, roofs, windows, floors, decorative window furnishings or treatments; treated glass covers for pictures, paintings, posters, and like display items; optical lenses; ophthalmic lenses; corrective ophthalmic lenses; implantable ophthalmic lenses; wall panels, and doors; counter tops; protected graphics; outdoor and indoor signs; enclosures, housings, panels, and parts for automatic teller machines (ATM); enclosures, housings, panels, and parts for lawn and garden tractors, lawn mowers, and tools, including lawn and garden tools; window and door trim; sports equipment and toys; enclosures, housings, panels, and parts for snowmobiles; recreational vehicle panels and components; playground equipment; shoe laces; articles made from plastic-wood combinations; golf course markers; utility pit covers; computer housings; desk-top computer housings; portable computer housings; lap-top computer housings; palm-held computer housings; monitor housings; printer housings; keyboards; FAX machine housings; copier housings; telephone housings; phone bezels; mobile phone housings; radio sender housings; radio receiver housings; light fixtures; lighting appliances; network interface device housings; transformer housings; air conditioner housings; cladding or seating for public transportation; cladding or seating for trains, subways, or buses; meter housings; antenna housings; cladding for satellite dishes; coated helmets and personal protective equipment; coated synthetic or natural textiles; coated photographic film and photographic prints; coated painted articles; coated dyed articles; coated fluorescent articles; coated foam articles; and like applications. The invention further contemplates additional fabrication operations on said articles, such as, but not limited to, molding, in-mold decoration, baking in a paint oven, lamination, and/or thermoforming.